1. Field of the Invention 
The present invention generally relates to electrical sensing devices. More particularly, this invention relates to a pressure transducer suitable for use in automotive applications, such as a switch sensor for a passive occupant detection system (PODS). 
2. Description of the Related Art 
PODS is a weight-based system for arming and disarming automotive passive restraint systems (e.g., air bags) in passenger vehicles to enable such systems to be effective for a range of occupant weights. Pressure or displacement transducers may be located in the passenger seat cushion and back for indicating if a seat is occupied and the weight of the occupant, e.g., an adult versus a child. Based on predetermined criteria, sensor output is used to control whether an air bag will deploy or not in the event  of the need for occupant restraint. PODS may be integrated with other sensing systems, such as ultrasonic sensors that provide additional information regarding the position of a passenger in a seat. 
Various types of pressure sensors are known, including micromachined single-crystal silicon pressure transducer cells manufactured using semiconductor fabrication processes. However, because of the brittle nature of the silicon materials, silicon sensors have found limited use for sensing force and displacement suitable for PODS applications. Other force and displacement-sensing transducers have been proposed, including those that make use of more rugged metal diaphragms, electrostatic or capacitive sensing structures, magnetic or ultrasonic measurement techniques, and compressible conductive gels. However, there remains a need for sensors that can be readily mass produced yet are capable of the high reliability and sensitivity required for PODS and other pressure-sensing applications. 